Stereo unit - poor sound

Me thinks you are confused here.

CDs are 44.1Khz, this is the SAMPLING rate, ie 44100 samples per second, this is fairly standard, there is also 32Khz, as used by nicam stereo TV, 48KHz used by higher end and prosumer audio stuff, and 96Khz, used in most pro end audio systems, and now 192Khz used in blueray.

the most common mistakes is using too low a BIT rate on your MP3, I would reccomend 256 as a good(ish) balance between quality and file size, 320 is the best, but also gives the largest file size, 192 is the minimum I would use, and even then only at a push, the bottom end is cut off more, and the top end becomes less crisp.

as to loosing volume, this is usually down the the converter rather than the actual conversion, alot of the converters result in a audio peak level of -4, I use exact audio copy (google for it) if just ripping a CD, this keeps the level as the original, although you may perceive a slight loss in volume due to the compression down to MP3. Good enough for in the car.

Ive not found an all in one solution yet, (ie rip, covert, normalise) but ideally the final MP3 needs to be "normalised" ie get the peak audio to 0db.

It does amuse me that for years people have been striving for better and better quality of sound, think cassette to CD etc, and now going backwards to highly compressed carp in MP3s AACs etc.

for those with cars with USB sockets, most of these will work an external hard drive, it just needs to be formatted in the FAT32 format, rather than the NTFS or other options vista/7 give you.

a 44.1 mp3 at 92Kb/s will still sound carp next to a 44.1 256KB/s mp3 (in fact a 32Khz @256 would sound better)